Helicobacter pylori has been epidemiologically linked with gastritis, gastric ulcers, and gastric neoplasia in humans. On the basis of the fact that H. pylori infection occurs naturally in rhesus macaques, the objective of this project is to investigate the feasibility of these nonhuman primates as a model of gastric H. pylori infection. We have used an isolate from a naturally infected animal in our colony (CRPRC) and a macaque derived isolate from another colony (kindly provided by A Dubois). Intragastric inoculation of two Helicobacter free rhesus macaques with a mixture of these two organisms resulted in mild infection which was demonstrated, using PCR techniques on organisms cultured from gastric biopsies, to be a monomorphic infection with the CRPRC derived strain. As an aid to large scale screening of animals for Helicobacter pylori infection, and to follow the status of inoculated animals, we have adapted the 14C-urea breath test to animals. H. pylori are urease producers which allows them to convert 14C-urea to ammonia and 14C-CO2. We administer 14C-urea via stomach tube to ketamine anesthetized animals equiped with a tracheal tube connected to a series of one-way valves which allow the animals to breath in room air and breathe out through a collection system which traps CO2. The latter is analyzed for 14C content to determine infection with H .pylori. These techniques will allow us subsequently to identify H. pylori negative animals, infect them with different strains of this organism (including strains isolated from humans), and follow the course of their infections during various manipulations designed to better understand the biology, treatment, and prevention of (infection with) this organism.